This invention relates to the electrolytic carboxylation of carbon acids and in particular to the use of electrogenerated bases as catalysts for the preparation of carboxylated carbon acids.
Electrochemical reduction of organic compounds often affords strongly basic and/or nucleophilic species, for example, carbanions, radical anions, dianions, and the like. The nucleophilic character of these species has been extensively exploited in many coupling, polymerization, and displacement reactions as reported in Organic Electrochemistry (Baizer, ed.) Marcel Dekker, New York, pp. 679-704; 947-974 and Baizer et al, Journal of Organic Chemistry, 37, 1951 (1972). However, their basicity has been used in synthesis only to a limited extent. For example, the synthetic utilization of electrogenerated bases in the Wittig reaction, the Stevens rearrangement, and the Michael addition reaction has been described, respectively, in Iversen et al, Tetrahedron Letters, 3523 (1969); Iversen, Tetrahedron Letters, 55 (1971); and Baizer et al, Tetrahedron Letters, 5209 (1973).
The progress of synthetic utilization of electrogenerated bases has been impeded by the usual requirement that the electrogenerated base must be present in stoichiometric amounts, an unappealingly wasteful and expensive requirement. And even in these reactions where the electrogenerated base need be present in only catalytic amounts, for example, the Michael addition reaction noted hereinabove, the utility of such bases has been severely limited in that little, if any, advantage is demonstrated over corresponding chemical procedures.
Furthermore, processes employing electrogenerated bases in carboxylation reactions have been glaringly unavailable, possibly because of the general expectation that such bases would successfully compete for the available in situ carbon dioxide with the anionic species which it is desired to carboxylate.
The difficulties and disadvantages encountered in the prior art processes of synthetic utilization of electrogenerated bases are overcome by the discovery that the electrolytic carboxylation of carbon acids is conveniently accomplished via electrogenerated bases to yield carboxylated carbon acids.